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#!/usr/bin/env python
"""
This is an example of "prompt_toolkit.contrib.regular_languages" which
implements a little calculator.
Type for instance::
> add 4 4
> sub 4 4
> sin 3.14
This example shows how you can define the grammar of a regular language and how
to use variables in this grammar with completers and tokens attached.
"""
import math
from prompt_toolkit import prompt
from prompt_toolkit.completion import WordCompleter
from prompt_toolkit.contrib.regular_languages.compiler import compile
from prompt_toolkit.contrib.regular_languages.completion import GrammarCompleter
from prompt_toolkit.contrib.regular_languages.lexer import GrammarLexer
from prompt_toolkit.lexers import SimpleLexer
from prompt_toolkit.styles import Style
operators1 = ["add", "sub", "div", "mul"]
operators2 = ["cos", "sin"]
def create_grammar():
return compile(
r"""
(\s* (?P<operator1>[a-z]+) \s+ (?P<var1>[0-9.]+) \s+ (?P<var2>[0-9.]+) \s*) |
(\s* (?P<operator2>[a-z]+) \s+ (?P<var1>[0-9.]+) \s*)
"""
)
example_style = Style.from_dict(
{
"operator": "#33aa33 bold",
"number": "#ff0000 bold",
"trailing-input": "bg:#662222 #ffffff",
}
)
if __name__ == "__main__":
g = create_grammar()
lexer = GrammarLexer(
g,
lexers={
"operator1": SimpleLexer("class:operator"),
"operator2": SimpleLexer("class:operator"),
"var1": SimpleLexer("class:number"),
"var2": SimpleLexer("class:number"),
},
)
completer = GrammarCompleter(
g,
{
"operator1": WordCompleter(operators1),
"operator2": WordCompleter(operators2),
},
)
try:
# REPL loop.
while True:
# Read input and parse the result.
text = prompt(
"Calculate: ", lexer=lexer, completer=completer, style=example_style
)
m = g.match(text)
if m:
vars = m.variables()
else:
print("Invalid command\n")
continue
print(vars)
if vars.get("operator1") or vars.get("operator2"):
try:
var1 = float(vars.get("var1", 0))
var2 = float(vars.get("var2", 0))
except ValueError:
print("Invalid command (2)\n")
continue
# Turn the operator string into a function.
operator = {
"add": (lambda a, b: a + b),
"sub": (lambda a, b: a - b),
"mul": (lambda a, b: a * b),
"div": (lambda a, b: a / b),
"sin": (lambda a, b: math.sin(a)),
"cos": (lambda a, b: math.cos(a)),
}[vars.get("operator1") or vars.get("operator2")]
# Execute and print the result.
print(f"Result: {operator(var1, var2)}\n")
elif vars.get("operator2"):
print("Operator 2")
except EOFError:
pass
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