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, j
from proveit.core_expr_types import Len, f_i_to_j, i_to_j_len
from proveit.logic import Equals, InSet
from proveit.numbers import Natural

# build up the expression from sub-expressions
expr = Lambda([f, i, j], Conditional(Equals(Len(operands = [f_i_to_j]), i_to_j_len), InSet(i_to_j_len, 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())

\left(f, i, j\right) \mapsto \left\{|\left(f\left(i\right), f\left(i + 1\right), \ldots, f\left(j\right)\right)| = \left(j - i + 1\right) \textrm{ if } \left(j - i + 1\right) \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	parameters: 1 body: 2
1	ExprTuple	25, 24, 20
2	Conditional	value: 3 condition: 4
3	Operation	operator: 5 operands: 6
4	Operation	operator: 7 operands: 8
5	Literal
6	ExprTuple	9, 10
7	Literal
8	ExprTuple	10, 11
9	Operation	operator: 12 operands: 13
10	Operation	operator: 14 operands: 15
11	Literal
12	Literal
13	ExprTuple	16
14	Literal
15	ExprTuple	20, 17, 18
16	ExprRange	lambda_map: 19 start_index: 24 end_index: 20
17	Operation	operator: 21 operand: 24
18	Literal
19	Lambda	parameter: 27 body: 23
20	Variable
21	Literal
22	ExprTuple	24
23	Operation	operator: 25 operand: 27
24	Variable
25	Variable
26	ExprTuple	27
27	Variable