All Questions
6
questions
4
votes
4
answers
191
views
How to use replacement rules in a named expression before a sub-expression evaluates?
I have a named expression: expr := a + b. a and b are also named expressions.
Let's say <...
3
votes
1
answer
98
views
Prevent argument substitution in held expression when injecting into unevaluated code
I want to write a custom sow/reap pair to wrap any piece of code in sow[code] and call reap ...
- 47.1k
10
votes
2
answers
1k
views
What is the Difference Between Rule (->) and RuleDelayed (:>)?
I am new to Mathematica so this question may seem rudimentary. Sorry for that! :)
I want to implement the well-known property of Kronecker's Delta
$$\Sigma_{i=1}^{n} a_i \delta_{ij}=a_j,\quad 1 \le ...
- 1,727
3
votes
0
answers
133
views
17
votes
1
answer
324
views
When is the righthand side of a RuleDelayed evaluated?
The documentation on RuleDelayed states that lhs :> rhs represents a rule that transforms lhs to rhs, evaluating rhs only after the rule is used.
Consider the ...
- 10.2k
106
votes
5
answers
6k
views
Replacement inside held expression
I wish to make a replacement inside a held expression:
f[x_Real] := x^2;
Hold[{2., 3.}] /. n_Real :> f[n]
The desired output is ...
- 62k