Expression of type Lambda

from the theory of proveit.numbers.negation

import proveit
# Automation is not needed when building an expression:
proveit.defaults.automation = False # This will speed things up.
proveit.defaults.inline_pngs = False # Makes files smaller.
%load_expr # Load the stored expression as 'stored_expr'
# import Expression classes needed to build the expression
from proveit import Conditional, Lambda, a, b
from proveit.logic import And, Equals, InSet
from proveit.numbers import Natural, Neg

# build up the expression from sub-expressions
expr = Lambda([a, b], Conditional(Equals(a, b), And(InSet(a, Natural), InSet(b, Natural), [Equals(Neg(a), Neg(b))])))

expr:

# check that the built expression is the same as the stored expression
assert expr == stored_expr
assert expr._style_id == stored_expr._style_id
print("Passed sanity check: expr matches stored_expr")

Passed sanity check: expr matches stored_expr

# Show the LaTeX representation of the expression for convenience if you need it.
print(stored_expr.latex())

\left(a, b\right) \mapsto \left\{a = b \textrm{ if } a \in \mathbb{N} ,  b \in \mathbb{N} ,  \left(\left(-a\right) = \left(-b\right)\right)\right..

stored_expr.style_options()

no style options

# display the expression information
stored_expr.expr_info()

	core type	sub-expressions	expression
0	Lambda	parameters: 4 body: 1
1	Conditional	value: 2 condition: 3
2	Operation	operator: 15 operands: 4
3	Operation	operator: 5 operands: 6
4	ExprTuple	22, 23
5	Literal
6	ExprTuple	7, 8, 9
7	Operation	operator: 11 operands: 10
8	Operation	operator: 11 operands: 12
9	ExprTuple	13
10	ExprTuple	22, 14
11	Literal
12	ExprTuple	23, 14
13	Operation	operator: 15 operands: 16
14	Literal
15	Literal
16	ExprTuple	17, 18
17	Operation	operator: 20 operand: 22
18	Operation	operator: 20 operand: 23
19	ExprTuple	22
20	Literal
21	ExprTuple	23
22	Variable
23	Variable