61 questions linked to/from Replacement inside held expression
340 views

HoldForm: how does it interact with nested evaluations?

Here's an example to illustrate the issue I'm having. right = 8 - y; left = y^2 + 6; integrand = HoldForm[Evaluate[right]] - HoldForm[Evaluate[left]] (I ...
239 views

Puzzled regarding avoiding evaluations and using results of computations as functions

What did I do before? I seem not to be able to understand MMA's evaluation scheme. I read some posts like Preventing Evaluation or a MathGroup post where the topics of evaluation prevention are ...
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How to use ReplaceAll and RuleDelayed with an Association? [duplicate]

I expected that something like this ...
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Replace inside a Held expression separate context

How do I replace content inside a Held expression without local values coming through? For example if you run the following code you get g[2] instead of ...
221 views

Replace variable with value prior to evaluating NIntegrate

The title says it all. Reading posts such as this however, I'm not seeing how to do this. This is the simplest example that can show my problem. ...
243 views

Instability, Courant Condition and Robustness about solving 2D+1 PDE

After several discussions, I would like to focus on the robustness of solving 2D+1 PDE by considering all suggested methods from @xzczd (see here) I found that the Ratio between the convection term ...
432 views

Condition and RuleDelayed

On this site I found, for example here, some very interesting questions and answers on the use of delayed rules with conditions. I would very much like to understand these answers, but so far I failed ...
896 views

Collect and simplify both the coefficents and the matched patterns

(This is a far tighter version of a previous question I asked) The problem with Collect is that while Collect[exp, pattern, Simplify] will simplify the coefficients,...
199 views

How I create a 'TraditionalForm' expression in which only parts are evaluated?

I have an expression for the form Subscript[W, f[a, b]][c] = ρ^f[a,b]ω[c]ρ^-f[a,b] that I want to render in TraditionalForm ...
196 views

KeyValuePattern in matching and replacement in nested associations

This case revealed I am missing something in pattern matching and evaluation in case of match, or I can't grasp it due to the busy week I have. Either way, I find this problem interesting for wider ...
175 views

Is Replace doing double work?

In an answer to this question, rm -rf used the function Replace with level spefication to do a series of replacements inside out. As far as I can see, the order of substitutions when more than one ...
1k views

Pass unevaluated function with evaluated arguments

I am almost sure that this question has been asked somewhere. I found similar ones, but I cannot find exactly what I need, which might mean that I am on the wrong track. I search a method to pass an ...