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Add StringTake with a string sequence. #1297

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Apr 22, 2021
Merged

Add StringTake with a string sequence. #1297

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3866c5c
Add StringTake with a string sequence.
rocky Apr 20, 2021
ae1f84d
Correct error results.
rocky Apr 21, 2021
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37 changes: 32 additions & 5 deletions mathics/builtin/strings.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2098,6 +2098,9 @@ class StringTake(Builtin):

<dt>'StringTake["$string$", {$m$, $n$, $s$}]'
<dd>gives characters $m$ through $n$ in steps of $s$.

<dt>'StringTake[{$s1$, $s2$, ...} $spec$}]'
<dd>gives the list of results for each of the $si$.
</dl>

>> StringTake["abcde", 2]
Expand All @@ -2113,6 +2116,10 @@ class StringTake(Builtin):
>> StringTake["abcdefgh", {1, 5, 2}]
= ace

Take the last 2 characters from several strings:
>> StringTake[{"abcdef", "stuv", "xyzw"}, -2]
= {ef, uv, zw}

StringTake also supports standard sequence specifications
>> StringTake["abcdef", All]
= abcdef
Expand All @@ -2127,17 +2134,26 @@ class StringTake(Builtin):
#> StringTake["abc", {0, 0}]
: Cannot take positions 0 through 0 in "abc".
= StringTake[abc, {0, 0}]

#> StringTake[{2, 4},2]
: String or list of strings expected at position 1.
= StringTake[{2, 4}, 2]

#> StringTake["kkkl",Graphics[{}]]
: Integer or a list of sequence specifications expected at position 2.
= StringTake[kkkl, -Graphics-]
"""

messages = {
"strse": "String expected at position 1.",
"mseqs": "Integer or list of two Intergers are expected at position 2.",
"strse": "String or list of strings expected at position 1.",
# FIXME: mseqs should be: Sequence specification (+n, -n, {+n}, {-n}, {m, n}, or {m, n, s}) or a list
# of sequence specifications expected at position 2 in
"mseqs": "Integer or a list of sequence specifications expected at position 2.",
"take": 'Cannot take positions `1` through `2` in "`3`".',
}

def apply(self, string, seqspec, evaluation):
"StringTake[string_, seqspec_]"

"StringTake[string_String, seqspec_]"
result = string.get_string_value()
if result is None:
return evaluation.message("StringTake", "strse")
Expand All @@ -2162,6 +2178,17 @@ def apply(self, string, seqspec, evaluation):

return String(result[py_slice])

def apply_strings(self, strings, spec, evaluation):
"StringTake[strings__, spec_]"
result_list = []
for string in strings.leaves:
result = self.apply(string, spec, evaluation)
if result is None:
return None
result_list.append(result)
return Expression("List", *result_list)



class StringDrop(Builtin):
"""
Expand Down Expand Up @@ -2192,7 +2219,7 @@ class StringDrop(Builtin):

messages = {
"strse": "String expected at position 1.",
"mseqs": "Integer or list of two Intergers are expected at position 2.",
"mseqs": "Integer or list of two Integers are expected at position 2.",
"drop": 'Cannot drop positions `1` through `2` in "`3`".',
}

Expand Down