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Add symbol end of file #1352

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Merged
rocky merged 2 commits into from
May 4, 2021
Merged

Add symbol end of file #1352

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SymbolEndOfFile = Symbol("EndOfFile")
rocky May 4, 2021
3fe0998
Go over Read documentation
rocky May 4, 2021
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53 changes: 38 additions & 15 deletions mathics/builtin/files_io/files.py
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Original file line number Diff line number Diff line change
Expand Up @@ -167,6 +167,8 @@ class EndOfFile(Builtin):
</dl>
"""

SymbolEndOfFile = Symbol("EndOfFile")


# TODO: Improve docs for these Read[] arguments.
class Byte(Builtin):
Expand Down Expand Up @@ -236,18 +238,24 @@ class Read(Builtin):
<dt>'Read[$stream$, $type$]'
<dd>reads the input stream and returns an object of the given type.

<dt>'Read[$stream$, $type$]'
<dd>reads the input stream and returns an object of the given type.

<dt>'Read[$stream$, Hold[Expression]]'
<dd>reads the input stream for an Expression and puts it inside 'Hold'.

</dl>
$type$ is one of:
<ul>
<li>Byte</li>
<li>Character</li>
<li>Expression</li>
<li>HoldExpression</li>
<li>Number</li>
<li>Real</li>
<li>Record</li>
<li>String</li>
<li>Word</li>
<li>Byte
<li>Character
<li>Expression
<li>HoldExpression
<li>Number
<li>Real
<li>Record
<li>String
<li>Word
</ul>

## Malformed InputString
Expand Down Expand Up @@ -330,12 +338,24 @@ class Read(Builtin):

## HoldExpression:
>> stream = StringToStream["2+2\\n2+3"];

'Read' with a 'Hold[Expression]' returns the expression it reads unevaluated so it can be later inspected and evaluated:

>> Read[stream, Hold[Expression]]
= Hold[2 + 2]

>> Read[stream, Expression]
= 5
>> Close[stream];

Reading a comment however will return the empy list:
>> stream = StringToStream["(* ::Package:: *)"];

>> Read[stream, Hold[Expression]]
= {}

>> Close[stream];

## Multiple types
>> stream = StringToStream["123 abc"];
>> Read[stream, {Number, Word}]
Expand Down Expand Up @@ -612,12 +632,12 @@ def reader(stream, word_separators, accepted=None):
nextline = next(read_record)
tmp = tmp + "\n" + nextline
except EOFError:
expr = Symbol("EndOfFile")
expr = SymbolEndOfFile
break
except Exception as e:
print(e)

if expr == Symbol("EndOfFile"):
if expr == SymbolEndOfFile:
evaluation.message(
"Read", "readt", tmp, Expression("InputSteam", name, n)
)
Expand All @@ -626,6 +646,9 @@ def reader(stream, word_separators, accepted=None):
if typ == Symbol("HoldExpression"):
expr = Expression("Hold", expr)
result.append(expr)
# else:
# TODO: Supposedly we can't get here
# what code should we put here?

elif typ == Symbol("Number"):
tmp = next(read_number)
Expand Down Expand Up @@ -663,7 +686,7 @@ def reader(stream, word_separators, accepted=None):
result.append(next(read_word))

except EOFError:
return Symbol("EndOfFile")
return SymbolEndOfFile
except UnicodeDecodeError:
evaluation.message("General", "ucdec")

Expand Down Expand Up @@ -1695,7 +1718,7 @@ def apply(self, name, n, typ, evaluation):
try:
result.append(self.readers[t](stream.io))
except struct.error:
result.append(Symbol("EndOfFile"))
result.append(SymbolEndOfFile)

if typ.has_form("List", None):
return Expression("List", *result)
Expand Down Expand Up @@ -2324,7 +2347,7 @@ def apply(self, channel, types, evaluation, options):
if tmp == SymbolFailed:
return

if tmp == Symbol("EndOfFile"):
if tmp == SymbolEndOfFile:
break
result.append(tmp)
return from_python(result)
Expand Down Expand Up @@ -2686,7 +2709,7 @@ def apply(self, name, n, types, m, evaluation, options):
return
for i in range(py_m):
result = super(Skip, self).apply(channel, types, evaluation, options)
if result == Symbol("EndOfFile"):
if result == SymbolEndOfFile:
return result
return SymbolNull

Expand Down