mem_fn() function
bind() is the topic of this section, which sits within the Function Objects module of Understanding Type Functions in C++.
A Heading That Names Two Functions
This article is about mem_fn(), but the supplied material is unusually thin, so it helps to start by reading exactly what it contains. The section is titled Using bind() Function, and it belongs to the Function Objects module of the chapter Understanding Type Functions in C++. The only other function named in the supplied material is mem_fn(), which appears on page 128 as a topic heading.
Before reading further, try to predict what a heading alone can tell you. Does a function's name tell you how it behaves? The rest of this article will test that question against the source.
Where These Functions Sit in the Module
Learning a function is easier when you know where it sits in the larger structure. In the supplied material, the chapter Understanding Type Functions in C++ contains a Function Objects module. Inside that module, the section on bind() is the topic of this lesson, and mem_fn() is a named function topic in the same module. The diagram below shows that placement.
Reading the diagram from the top down gives you the context you need. The chapter is the outer container. The Function Objects module is one part of it. Both bind() and mem_fn() are entries inside that module. The source does not say that mem_fn() is a subtopic of bind(), or the reverse. They are placed side by side.
What the Source Establishes About bind()
The section titled Using bind() Function tells you what the learner is expected to pick up: how to use bind() as a tool inside the broader topic of function objects. That is the full extent of what the supplied material states about bind(). The excerpt gives the section heading and its place in the module, but it does not include a definition, a syntax template, or a worked example for bind().
- Established:
bind()is the topic of the section Usingbind()Function. - Established: that section sits within the Function Objects module of Understanding Type Functions in C++.
- Not established by the supplied excerpt: what
bind()does, how it is called, or what its arguments mean. - Where to find those details: the full chapter text, which the source says should be used to learn
bind().
What the Source Establishes About mem_fn()
mem_fn() is a named function topic in the Function Objects module of Understanding Type Functions in C++. It appears on page 128 of the source as a heading, and the material refers to the mem_fn() function.
What do you think happens?
Does the supplied source explain what mem_fn() does when it is called?
Reveal answer
No, it only names mem_fn() as a heading on page 128.
The supplied excerpt contains no definition, syntax, or example for mem_fn(). Any behavior would have to come from the full source text at that page.
Because mem_fn() is the one function named alongside this section, the source treats it as a companion topic. The excerpt does not spell out the relationship between the two functions. The concept map below shows what is and is not known.
Mistakes When Reading a Function Name
Common mistake Assuming mem_fn() behaves a certain way because of its name
What it looks likeConcluding from the name alone how mem_fn() should be called or what it returns.
Why it failsThe source names
mem_fn()as a heading but does not define or demonstrate it. The source says behavior should be learned from the full explanation, not inferred from the name.Do this insteadRead the full source explanation at the relevant page before describing how mem_fn() works.
Common mistake Treating the section heading as an explanation
What it looks likeBelieving that because the section is titled Using bind() Function, the section already explains how to use bind().
Why it failsA section heading identifies a topic. It does not explain how the function behaves.
Do this insteadUse the section heading to find the topic, then read the body text for the actual explanation.
Common mistake Deciding bind() and mem_fn() are the same kind of thing without checking
Why it failsThe excerpt places them side by side inside the same module but does not state how they are related.
Do this insteadKeep them as distinct topics until the full text shows the relationship.
Verifying mem_fn() in the Primary Source
Because the excerpt gives only a heading, a learner who wants accurate details about mem_fn() must go back to the primary source. The steps below follow the guidance in the supplied material: locate the module, find the heading, read the full text, and rely only on what that text says.
Using only the supplied excerpt, write two sentences: one stating what is established about mem_fn(), and one stating what the excerpt leaves for you to check in the full source.
Hints
- The excerpt establishes that
mem_fn()is a named function topic in the Function Objects module, appearing on page 128. - The excerpt does not include a definition, syntax, or example for
mem_fn().
Recording What You Know and What You Still Need
Key Takeaways
bind()is the topic of the section Usingbind()Function, which sits within the Function Objects module of Understanding Type Functions in C++.mem_fn()is a named function topic in the same module, appearing on page 128, and it is named alongside thebind()section in the supplied material.- The supplied excerpt does not define, demonstrate, or give syntax for either
bind()ormem_fn(), so their behavior must be taken from the full source text. - Do not infer how
mem_fn()behaves from its name. Locate the heading, read the full explanation at that page, and record claims with their page references.