Expression of type Equals

from the theory of proveit.numbers.addition

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 ExprRange, IndexedVar, Lambda, Variable, a, b
from proveit.core_expr_types import Len
from proveit.logic import Equals
from proveit.numbers import one, three

# build up the expression from sub-expressions
sub_expr1 = Variable("_b", latex_format = r"{_{-}b}")
sub_expr2 = Variable("_a", latex_format = r"{_{-}a}")
expr = Equals(Len(operands = [Lambda(sub_expr1, a), Lambda(sub_expr1, b), Lambda(sub_expr2, IndexedVar(a, sub_expr2))]), Len(operands = [ExprRange(sub_expr2, sub_expr2, one, three)]))

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({_{-}b} \mapsto a, {_{-}b} \mapsto b, {_{-}a} \mapsto a_{{_{-}a}}\right)| = |\left(1, 2, \ldots, 3\right)|

stored_expr.style_options()

name	description	default	current value	related methods
operation	'infix' or 'function' style formatting	infix	infix
wrap_positions	position(s) at which wrapping is to occur; '2 n - 1' is after the nth operand, '2 n' is after the nth operation.	()	()	('with_wrapping_at', 'with_wrap_before_operator', 'with_wrap_after_operator', 'without_wrapping', 'wrap_positions')
justification	if any wrap positions are set, justify to the 'left', 'center', or 'right'	center	center	('with_justification',)
direction	Direction of the relation (normal or reversed)	normal	normal	('with_direction_reversed', 'is_reversed')

# display the expression information
stored_expr.expr_info()

	core type	sub-expressions	expression
0	Operation	operator: 1 operands: 2
1	Literal
2	ExprTuple	3, 4
3	Operation	operator: 6 operands: 5
4	Operation	operator: 6 operands: 7
5	ExprTuple	8, 9, 10
6	Literal
7	ExprTuple	11
8	Lambda	parameter: 18 body: 19
9	Lambda	parameter: 18 body: 13
10	Lambda	parameter: 21 body: 14
11	ExprRange	lambda_map: 15 start_index: 16 end_index: 17
12	ExprTuple	18
13	Variable
14	IndexedVar	variable: 19 index: 21
15	Lambda	parameter: 21 body: 21
16	Literal
17	Literal
18	Variable
19	Variable
20	ExprTuple	21
21	Variable