Accessing Input Elements

When dealing with complex input formats, attaching constraints can be complex, as elements can occur multiple times in a generated input. Fandango offers a few mechanisms to disambiguate these, and to specify specific contexts in which to search for elements.

Derivation Trees

So far, we have always assumed that Fandango generates strings from the grammar. Behind the scenes, though, Fandango creates a far richer data structure - a so-called derivation tree that maintains the structure of the string and allows accessing individual elements. Every time Fandango sees a grammar rule

<symbol> ::= ...

it generates a derivation tree whose root is <symbol> and whose children are the elements of the right-hand side of the rule.

Let’s have a look at our persons.fan spec:

<start> ::= <person_name> "," <age>
<person_name> ::= <first_name> " " <last_name>
<first_name> ::= <name>
<last_name> ::= <name>
<name> ::= <ascii_uppercase_letter><ascii_lowercase_letter>+
<age> ::= <digit>+

The <start> rule says

<start> ::= <person_name> "," <age>

Then, a resulting derivation tree for <start> looks like this:

As Fandango expands more and more symbols, it expands the derivation tree accordingly. Since the grammar definition for <person_name> says

<person_name> ::= <first_name> " " <last_name>

the above derivation tree would be extended to

And if we next extend <age> and then <digit> based on their definitions

<age> ::= <digit>+

If one has a Kleene operator like +, *, or ?, the elements operated on become children of the symbol being defined. Hence, the <digit> elements become children of the <age> symbol.

our tree gets to look like this:

Repeating the process, it thus obtains a tree like this:

Note how the tree records the entire history of how it was created - how it was derived, actually.

To obtain a string from the tree, we traverse its children left-to-right, ignoring all nonterminal symbols (in <...>) and considering only the terminal symbols (in quotes). This is what we get for the above tree:

Ex Pltz,18

And this is the string Fandango produces. However, viewing the Fandango results as derivation trees allows us to access elements of the Fandango-produced strings and to express constraints on them.

Diagnosing Derivation Trees

To examine the derivation trees that Fandango produces, use the --format=grammar output format. This produces the output in a grammar-like format, where children are indented under their respective parents. As an example, here is how to print a derivation tree from persons.fan:

$ fandango fuzz -f persons.fan -n 1 --format=grammar

<start> ::= <person_name> ',' <age>  # Position 0x0000 (0); Hqwlsxsvunuqlykmguykt Yxvrkmdcyviqthymndxy,6053337261160
  <person_name> ::= <first_name> ' ' <last_name>  # Position 0x0001 (1); Hqwlsxsvunuqlykmguykt Yxvrkmdcyviqthymndxy
    <first_name> ::= <name>
      <name> ::= <ascii_uppercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter>  # Hqwlsxsvunuqlykmguykt
        <ascii_uppercase_letter> ::= <_ascii_uppercase_letter>
          <_ascii_uppercase_letter> ::= 'H'  # Position 0x0002 (2)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'q'  # Position 0x0003 (3)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'w'  # Position 0x0004 (4)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'l'  # Position 0x0005 (5)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 's'  # Position 0x0006 (6)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'x'  # Position 0x0007 (7)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 's'  # Position 0x0008 (8)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'v'  # Position 0x0009 (9)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'u'  # Position 0x000a (10)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'n'  # Position 0x000b (11)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'u'  # Position 0x000c (12)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'q'  # Position 0x000d (13)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'l'  # Position 0x000e (14)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'y'  # Position 0x000f (15)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'k'  # Position 0x0010 (16)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'm'  # Position 0x0011 (17)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'g'  # Position 0x0012 (18)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'u'  # Position 0x0013 (19)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'y'  # Position 0x0014 (20)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'k'  # Position 0x0015 (21)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 't'  # Position 0x0016 (22)
    <last_name> ::= <name>
      <name> ::= <ascii_uppercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter> <ascii_lowercase_letter>  # Yxvrkmdcyviqthymndxy
        <ascii_uppercase_letter> ::= <_ascii_uppercase_letter>
          <_ascii_uppercase_letter> ::= 'Y'  # Position 0x0017 (23)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'x'  # Position 0x0018 (24)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'v'  # Position 0x0019 (25)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'r'  # Position 0x001a (26)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'k'  # Position 0x001b (27)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'm'  # Position 0x001c (28)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'd'  # Position 0x001d (29)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'c'  # Position 0x001e (30)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'y'  # Position 0x001f (31)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'v'  # Position 0x0020 (32)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'i'  # Position 0x0021 (33)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'q'  # Position 0x0022 (34)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 't'  # Position 0x0023 (35)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'h'  # Position 0x0024 (36)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'y'  # Position 0x0025 (37)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'm'  # Position 0x0026 (38)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'n'  # Position 0x0027 (39)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'd'  # Position 0x0028 (40)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'x'  # Position 0x0029 (41)
        <ascii_lowercase_letter> ::= <_ascii_lowercase_letter>
          <_ascii_lowercase_letter> ::= 'y'  # Position 0x002a (42)
  <age> ::= <digit> <digit> <digit> <digit> <digit> <digit> <digit> <digit> <digit> <digit> <digit> <digit> <digit>  # 6053337261160
    <digit> ::= <_digit>
      <_digit> ::= '6'  # Position 0x002b (43)
    <digit> ::= <_digit>
      <_digit> ::= '0'  # Position 0x002c (44)
    <digit> ::= <_digit>
      <_digit> ::= '5'  # Position 0x002d (45)
    <digit> ::= <_digit>
      <_digit> ::= '3'  # Position 0x002e (46)
    <digit> ::= <_digit>
      <_digit> ::= '3'  # Position 0x002f (47)
    <digit> ::= <_digit>
      <_digit> ::= '3'  # Position 0x0030 (48)
    <digit> ::= <_digit>
      <_digit> ::= '7'  # Position 0x0031 (49)
    <digit> ::= <_digit>
      <_digit> ::= '2'  # Position 0x0032 (50)
    <digit> ::= <_digit>
      <_digit> ::= '6'  # Position 0x0033 (51)
    <digit> ::= <_digit>
      <_digit> ::= '1'  # Position 0x0034 (52)
    <digit> ::= <_digit>
      <_digit> ::= '1'  # Position 0x0035 (53)
    <digit> ::= <_digit>
      <_digit> ::= '6'  # Position 0x0036 (54)
    <digit> ::= <_digit>
      <_digit> ::= '0'  # Position 0x0037 (55)

We see how the produced derivation tree consists of a <start> symbol, whose <first_name> and <last_name> children expand into <name> and letters; the <age> symbol expands into <digit> symbols.

The comments (after #) show the individual positions into the input, as well as the values of compound symbols.

What is the full string represented by the above derivation tree?

Solution

You can find on the right-hand side of the first line.

Tip

The --format=grammar option is great for debugging, especially binary formats.

Specifying Paths

One effect of Fandango producing derivation trees rather than “just” strings is that we can define special operators that allow us to access subtrees (or sub-elements) of the produced strings - and express constraints on them. This is especially useful if we want constraints to apply only in specific contexts - say, as part of some element <a>, but not as part of an element <b>.

Accessing Children

These selectors are similar to XPath, but better aligned with Python. In XPath, the first child has the index 1, in Fandango, it has the index 0.

The expression <foo>[N] accesses the N-th child of <foo>, starting with zero.

If <foo> is defined in the grammar as

<foo> ::= <bar> ":" <baz>

then <foo>[0] returns the <bar> element, <foo>[1] returns ":", and <foo>[2] returns the <baz> element.

In our persons.fan derivation tree for Ex Pltz, for instance, <start>[0] would return the <person_name> element ("Ex Pltz"), and <start>[2] would return the <age> element (18).

We can use this to access elements in specific contexts. For instance, if we want to refer to a <name> element, but only if it is the child of a <first_name> element, we can refer to it as <first_name>[0] - the first child of a <first_name> element:

<first_name> ::= <name>

Here is a constraint that makes Fandango produce first names that end with x:

Since a <first_name> is defined to be a <name>, we could also write <first_name>.endswith("x")

$ fandango fuzz -f persons.fan -n 10 -c '<first_name>[0].endswith("x")'

Uanaapvx Jitzsdtoymmkydadsnxa,76527161108

Jmlullnnx Mmrbvjk,41121589

Iwgbbcctrbkrgainrx Clefruyvoofqb,153

Dyzmzknvsffzzgawrfmrx Arokwrvd,029436655949676359

Tmox Axrbywhrgb,9596515226924237
Fqxqqclljrjbeeicsuvx Suaucvfug,37058527359348758

Nqxqqclljrjbeeicsuvx Suaucvfug,37058527359348758

Dyzmzknvsffzzgawrfmrx Arokwrvd,9596515226924237
Tmox Axrbywhrgb,029436655949676359

Uanaapvx Yacxfhurkgext,368566900323

Tip

As in Python, you can use negative indexes to refer to the last elements. <age>[-1], for instance, gives you the last child of an <age> subtree.

Important

While symbols act as strings in many contexts, this is where they differ. To access the first character of a symbol <foo>, you need to explicitly convert it to a string first, as in str(<foo>)[0].

Slices

The Fandango slices maintain the property that <name>[n:m] = <name>[n] + <name>[n + 1] + … + <name>[m - 1], which holds for all sequences in Python.

Fandango also allows you to use Python slice syntax to access multiple children at once. <name>[n:m] returns a new (unnamed) root which has <name>[n], <name>[n + 1], …, <name>[m - 1] as children. This is useful, for instance, if you want to compare several children against a string:

$ fandango fuzz -f persons-faker.fan -n 10 -c '<name>[0:2] == "Ch"'

Christina Chavez,22

Charles Chavez,8673

Christina Chavez,3398390944

Christina Chavez,3398320944
Christina Chavez,5973452237244
Charles Chavez,3398390944

Christina Chavez,92
Christina Chavez,3398390244
Charles Chavez,88071644176369237
Christina Chavez,82285715

Would one also be able to use <start>[0:2] == "Ch" to obtain inputs that all start with "Ch"?

Solution

No, this would not work. Remember that in derivation trees, indexes refer to children, not characters. So, according to the rule

<start> ::= <person_name> "," <age>

<start>[0] is a <person_name>, <start>[1] is a ",", and <start>[2] is an <age>. Hence, <start>[0:2] refers to <start> itself, which cannot be "Ch".

Indeed, to have the string start with "Ch", you (again) need to convert <start> into a string first, and then access its individual characters:

$ fandango fuzz -f persons-faker.fan -n 10 -c 'str(<start>)[0:2] == "Ch"'

Christine Bates,80163694372345521

Christine Warren,989824713

Christian Benitez,13351

Christina Herrera,70573837

Christopher Aguirre,490654145515540
Cheryl Golden,1395720261

Christina Williams,05125724

Cheryl Golden,218180618505
Christina Herrera,70573137
Christina Williams,35125724

The Fandango slices maintain the property that <name>[i:] + <name>[:i] = <name>

Fandango supports the full Python slice semantics:

• An omitted first index defaults to zero, so <foo>[:2] returns the first two children.

• An omitted second index defaults to the size of the string being sliced, so <foo>[2:] returns all children starting with <foo>[2].

• Both the first and the second index can be negative again.

Selecting Children

Referring to children by number, as in <foo>[0], can be a bit cumbersome. This is why in Fandango, you can also refer to elements by name.

In XPath, the corresponding operator is /.

The expression <foo>.<bar> allows accessing elements <bar> when they are a direct child of a symbol <foo>. This requires that <bar> occurs in the grammar rule defining <foo>:

<foo> ::= ...some expansion that has <bar>...

To refer to the <name> element as a direct child of a <first_name> element, you thus write <first_name>.<name>. This allows you to express the earlier constraint in a possibly more readable form:

$ fandango fuzz -f persons.fan -n 10 -c '<first_name>.<name>.endswith("x")'

Xtogsajlyvgnvqmwcbx Sacohkrzwjyiafsl,74055797092410856972

Pdkx Rzmbnrnycbmwfy,780847633

Gzkwxyxjvodkwpdtx Xlxmcapfwjygw,708162

Pdkx Rzmbnrnucbmwfy,780847633

Pdkx Qosdjlanbapqcmhe,780847633
Gzkwxyxjvodkwpdtx Sfmjkycdakttsnvjfef,1623

Xtogsajlyxgnvqmwcbx Sacohkrzwjyiafsl,74055797092410856972
Pdkx Rzmbnrnycbmwfy,543362470

Pdkx Rzmbnrnycbmwfy,780847638

Pdkx Vzmbnrnycbmwfy,780847633

Note

You can only access nonterminal children this way; <person_name>." " (the space in the <person_name>) gives an error.

Selecting Descendants

Often, you want to refer to elements in a particular context set by the enclosing element. This is why in Fandango, you can also refer to descendants.

In XPath, the corresponding operator is //.

The expression <foo>..<bar> allows accessing elements <bar> when they are a descendant of a symbol <foo>. <bar> is a descendant of <foo> if

<foo>..<bar> includes <foo>.<bar>.

• <bar> is a child of <foo>; or

• one of <foo>’s children has <bar> as a descendant.

If that sounds like a recursive definition, that is because it is. A simpler way to think about <foo>..<bar> may be “All <bar>s that occur within <foo>”.

Let us take a look at some rules in our persons.fan example:

<first_name> ::= <name>
<last_name> ::= <name>
<name> ::= <ascii_uppercase_letter><ascii_lowercase_letter>+
<ascii_uppercase_letter> ::= "A" | "B" | "C" | ... | "Z"

To refer to all <ascii_uppercase_letter> element as descendant of a <first_name> element, you thus write <first_name>..<ascii_uppercase_letter>.

Hence, to make all uppercase letters X, but only as part of a first name, you may write

$ fandango fuzz -f persons.fan -n 10 -c '<first_name>..<ascii_uppercase_letter> == "X"'

Xbyqyyyajyiul Egm,213658870498
Xugydvatq Aipse,223701295391742

Xievoufnytqyrilcyaako Lhvnjzhklbwqbqx,47014840013990229085
Xckglktsfqibzwrrru Xmgbuknaoevgfcx,6913353369010
Xwpfk Etsgeuofsuvdqgqvoyg,12742241

Xmfqejlzibgtnrihzux Zgtsllwhefj,7163238338
Xeaexfz Jickwpo,645092

Xpkfgkpearvzg Bwtzhflsrrjyxslfmnc,59216
Xyivgwyeaehyatwsq Lequ,9597147877

Xpsenjhuuccsdzpbsghl Msdgduavfbbwvuegxd,672248330725064

Chains

You can freely combine [], ., and .. into chains that select subtrees. What would the expression <start>[0].<last_name>..<ascii_lowercase_letter> refer to, for instance?

Solution

This is easy:

• <start>[0] is the first element of start, hence a <person_name>.

• .<last_name> refers to the child of type <last_name>

• ..<ascii_lowercase_letter> refers to all descendants of type <ascii_lowercase_letter>

Let’s use this in a constraint:

$ fandango fuzz -f persons.fan -n 10 -c '<start>[0].<last_name>..<ascii_lowercase_letter> == "x"'

Ppfdaxuvyt Ixxxxxxxxxxxxxxx,4577906325524

Bacftrlmsd Rx,57
Cpnhrp Dxxxx,963202213

Qoftdykijjorchodb Zxxxxxxxxxxxxxxxxxx,477526224435830773
Svodethpcy Sxxxx,6838
Qebarssctqulxgcmmmtnt Rx,867946074

Wv Jxxxxxxxxxxxxxxxxxxxx,772358047362

Navqrqjsspa Vxxxxxxxxxxxx,60616790521205358231
Mttonpyponaliofexuo Kxxxxxxxxxx,44
Ajlitqxqprpstse Vxx,64787

Quantifiers

By default, whenever you use a symbol <foo> in a constraint, this constraint applies to all occurrences of <foo> in the produced output string. For your purposes, though, one such instance already may suffice. This is why Fandango allows expressing quantification in constraints.

Star Expressions

In Fandango, you can prefix an element with * to obtain a collection of all these elements within an individual string. Hence, *<name> is a collection of all <name> elements within the generated string. This syntax can be used in a variety of ways. For instance, we can have a constraint check whether a particular element is in the collection:

Not every constraint that can be expressed also can be solved by Fandango.

"Pablo" in *<name>

This constraint evaluates to True if any of the values in *<name> (= one of the two <name> elements) is equal to "Pablo". *-expressions are mostly useful in quantifiers, which we discuss below.

Existential Quantification

To express that within a particular scope, at least one instance of a symbol must satisfy a constraint, use a *-expression in combination with any():

any(CONSTRAINT for ELEM in *SCOPE)

where

• SCOPE is a nonterminal (e.g. <age>);

• ELEM is a Python variable; and

• CONSTRAINT is a constraint over ELEM

Hence, the expression

any(n.startswith("A") for n in *<name>)

ensures there is at least one element <name> that starts with an “A”:

Let us decompose this expression for a moment:

• The expression for n in *<name> lets Python iterate over *<name> (all <name> objects within a person)…

• … and evaluate n.startswith("A") for each of them, resulting in a collection of Boolean values.

• The Python function any(list) returns True if at least one element in list is True.

So, what we get is existential quantification:

$ fandango fuzz -f persons.fan -n 10 -c 'any(n.startswith("A") for n in *<name>)'

Dxshgjgsfafy Aqjneruwqb,690330212470731956

Aevw Yyrhxiuzmxucckk,5360881203261552

Lz Aifynswnappel,61245749411952

Ad Pd,66

Aqpvbjw Efolgscxiaciswnucfiq,396415779917237

Adwwjjrgqw Tu,931823168787150457

Zlhfdwaqdudkpqn Aar,764270931

Vupyifjmypq Adhvcnccuevngwsobycpo,12278

Dxshgjgsfafy Aqjneruwqb,790330212470731956
Vupyifjmypq Adhvcnccuevngwsobycpo,12268

Universal Quantification

Where there are existential quantifiers, there also are universal quantifiers. Here we use the Python all() function; all(list) evaluates to True only if all elements in list are True.

We use a *-expression in combination with all():

all(CONSTRAINT for ELEM in *SCOPE)

Hence, the expression

all(c == "a" for c in *<first_name>..<ascii_lowercase_letter>)

ensures that all sub-elements <ascii_lowercase_letter> in <first_name> have the value “a”.

Again, let us decompose this expression:

• The expression for c in *<first_name>..<ascii_lowercase_letter> lets Python iterate over all <ascii_lowercase_letter> objects within <first_name>…

• … and evaluate c == "a" for each of them, resulting in a collection of Boolean values.

• The Python function all(list) returns True if all elements in list are True.

So, what we get is universal quantification:

$ fandango fuzz -f persons.fan -n 10 -c 'all(c == "a" for c in *<first_name>..<ascii_lowercase_letter>)'

Uaa Jn,460150152419570
Daaaaaaaaaaaaaaaa Dlighxkilfcsefeuo,69848569030032113

Zaa Hgqwgrmyckorvnljcdqx,54245624871842825874

Gaaaaaaaaaaaaaaa Pnlaebhmsgdnwebdsful,9796995032836854
Waa Rnzjzbewtkisoooypb,759696180

Jaaaaaaaaaa Choahqnysahxpgykk,7864921328866222817
Caaaaaaaaaaaaaaa Zdn,935884568703

Saaaaaaaaaaaaaaa Ufxqpqrxykxcr,4589036524905512033
Baaaaaaaaaa Scevfebnvlaiphgsiotm,89767173530729525

Kaaa Jyw,99757296883357893

By default, all symbols are universally quantified within <start>, so a dedicated universal quantifier is only needed if you want to limit the scope to some sub-element. This is what we do here with <first_name>..<ascii_lowercase_letter>, limiting the scope to <first_name>.

Given the default universal quantification, you can actually achieve the same effect as above without all() and without a *. How?

Solution

You can access all <ascii_lowercase_letter> elements within <first_name> directly:

$ fandango fuzz -f persons.fan -n 10 -c '<first_name>..<ascii_lowercase_letter> == "a"'

Old-Style Quantifiers

Prior to version 1.0, Fandango supported another style of quantifiers:

• The expression forall SYMBOL in EXPRESSION: CONSTRAINT is equivalent to all(CONSTRAINT for ELEM in *EXPRESSION: )

• The expression exists SYMBOL in EXPRESSION: CONSTRAINT is equivalent to any(CONSTRAINT for ELEM in *EXPRESSION: )

with SYMBOL being a symbol (in <...>, so not a Python object) which can be referred to in CONSTRAINT.

To express that at least one letter in <first_name> should be 'a', write

exists <c> in <first_name>: str(<c>) == 'a'

$ fandango fuzz -f persons.fan -n 5 -c 'exists <c> in <ascii_lowercase_letter>: str(<c>) == "a"'

Uaaada Qaajafaa,59669718079

Baaaaaahaqaaasapgas Fzabaaa,7739178158194929766
Kaaaaa Pgaa,3156249685370803
Obtmvjagcmacfedil Nwxgkffok,45
Oaaaaaaaamacaaaaa Naagaffak,45

$ fandango fuzz -f persons.fan -n 5 -c 'forall <c> in <ascii_lowercase_letter>: str(<c>) == "a"'

Xa Raa,8121

Vaaaa Aaa,745635094982686

Ga Ga,215107111692515
Caaaaa Caa,231

Ga Ga,0246

Deprecated since version 1.0: Old-style quantifiers will be deprecated in a future Fandango version. Use all() and any() instead.