Expression of type Lambda

from the theory of proveit.core_expr_types.tuples

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, f, i
from proveit.core_expr_types import Len, f_1_to_i
from proveit.logic import Equals, Forall, InSet
from proveit.numbers import Natural

# build up the expression from sub-expressions
expr = Lambda(i, Conditional(Forall(instance_param_or_params = [f], instance_expr = Equals(Len(operands = [f_1_to_i]), i)), InSet(i, Natural)))

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())

i \mapsto \left\{\forall_{f}~\left(|\left(f\left(1\right), f\left(2\right), \ldots, f\left(i\right)\right)| = i\right) \textrm{ if } i \in \mathbb{N}\right..

stored_expr.style_options()

no style options

# display the expression information
stored_expr.expr_info()

	core type	sub-expressions	expression
0	Lambda	parameter: 21 body: 2
1	ExprTuple	21
2	Conditional	value: 3 condition: 4
3	Operation	operator: 5 operand: 9
4	Operation	operator: 7 operands: 8
5	Literal
6	ExprTuple	9
7	Literal
8	ExprTuple	21, 10
9	Lambda	parameter: 23 body: 12
10	Literal
11	ExprTuple	23
12	Operation	operator: 13 operands: 14
13	Literal
14	ExprTuple	15, 21
15	Operation	operator: 16 operands: 17
16	Literal
17	ExprTuple	18
18	ExprRange	lambda_map: 19 start_index: 20 end_index: 21
19	Lambda	parameter: 25 body: 22
20	Literal
21	Variable
22	Operation	operator: 23 operand: 25
23	Variable
24	ExprTuple	25
25	Variable